Purine catabolism refers to biochemical pathways by which ribonucleotides are degraded to uric acid in human tissues. Acquired disorders of nucleotide catabolism may be a common clinical occurrence in acutely ill patients. In the present study, the regulation of purine catabolism is to be examined in normal and disease states. The approach is to include sophisticated biochemical techniques and detailed clinical observations. The proposed research will include: a) a detailed study of a model of ribonucleotide catabolism in diploid fibroblasts designed to characterize the regulation of the pathway, to explore its disorders and to design methods for their modification; b) to purify and study in detail the kinetic and regulatory properties of certain important enzymes of purine catabolism; c) to evaluate in depth fructose-induced purine catabolism, a model of nucleotide degradation in man, in normal subjects and in patients with inborn errors of purine metabolism; d) to establish convincing evidence for activation of purine catabolism in critically ill patients; and e) to explore potential therapies in vivo and in vitro. Specific methods of procedure will include techniques for enzyme purification (ion exchange chromatography, gel filtration, isoelectric focusing, affinity chromatography), enzyme immunoprecipitation and enzymatic and spectrophotometric assays of purine intermediates. It is hoped that the biochemical observations will form the basis for elucidating the clinical phenomenon studied. An understanding of the pathophysiological basis of disordered purine catabolism in clinical disease states may faclitate the development of innovative therapeutic approaches.